Characteristic symptoms of Parkinson's disease, which, for that matter, need not occur all at the same time, include: shaking, muscular rigidity and paucity of movement. This does not involve palsy but a (temporary) disturbance of muscle controls and of muscle coordination. The cause is degeneration of areas in the brain, specifically the "black nuclei" and the "basal brain", as a result of which insufficient neurotransmitter (dopamine) is produced. These areas of the brain are of vital importance for a smooth performance of movements, i.e. for an effortless initiation of a movement, proper control during the movement, and the termination of the movement. These areas further ensure that when the flexors of a limb are to contract, the extensors relax at the same time. This interaction is of importance for a smooth performance of to-and-fro movements, as during eating, writing, handiwork, getting dressed and undressed. These are the first movements to present problems in Parkinson's disease. When the performance of the movements no longer proceeds automatically, it will be attempted to perform them more deliberately, which requires an effort.
This most conspicuous symptom of Parkinson's disease, i.e. shaking (tremor), involves an involuntary rhythmic movement of a number of muscles, mostly of one or both hands. This movement is most clearly visible if the hand is at rest. The frequency of this so-called rest tremor is 4-7 Hz. During sleep the tremor does not occur and emotions may aggravate the tremor distinctly.
Another symptom is muscular rigidity. Such rigidity, also referred to as hypertonia, arises in that the muscles are continuously in a state of slight contraction and this rigidity must be overcome before a movement can be initiated.
The third symptom mentioned, paucity of movement (hypokinesia), is a result of the muscular rigidity. Fine to-and-fro movements, as in tying shoe-laces, are more difficult to perform.
There are not as yet any medicines to cure the disease. Treatment is primarily focused on removing complaints. Thus, the deficiency of neurotranamitter (such as dopamine) is supplemented by medicines. Further, the symptoms of the disease can be suppressed by surgical intervention in the brain, which is obviously a hazardous enterprise.
As already observed in the foregoing, writing can present problems. Indeed, writing is a complex process that proceeds automatically under normal circumstances. It refires the hand muscles to be supple and a proper coordination of the fine movements. In Parkinson's disease this coordination is disturbed, and patients experience this as a major drawback.
Accordingly, a need exists for writing implements whereby this drawback is eliminated as far as possible. A known proposal towards facilitating writing for patients suffering from muscular diseases, including Parkinson patients, concerns the ergonomics of the writing pen. A slender pen is more difficult to hold and aggravates tremor. Using a pen with a spherical grip which can be embraced by the hand with a good fit enables writing from the wrist. Another known proposal involves a so-called soft grip, i.e. a flexible sleeve which can be fitted over a pen and has a lobed configuration, viewed in cross section, which urges the writing fingers in the correct position and provides a proper hold without effort.
German patent application 1611549 (Brown et al) and European patent application 0569638 (Hart Enterprises) disclose marker or decoration pens in the toy domain, which are provided with means for setting the pen into vibration.
They have in common that the eccentric weight is provided at the rear end of the pen and that an eccentric oscillating movement is thereby generated also at the rear end of the drawing implement, such that when the pen is moved along a straight line over the paper, the entire pen oscillates, with the part held by the fingers being the fulcrum, and the writing end makes an opposite oscillating movement. If the pen, as is commonly done, in held obliquely to the paper and a pulling movement over the paper is performed, the result will be a decorative, repetitive loop pattern.
The known pens are neither designed nor suitable for producing normal handwriting. Writing with them is even virtually impossible.